1. Field of the Invention
The present invention is related to a negative-pressure control device for an ink-supply system, and especially to a structure provided with a negative-pressure ink-jet pipeline to prevent leakage of ink in an ink-jet head, and when the ink-jet head do jet printing downwards, it makes a predetermined amount of ink in the ink-supply structure flow into the ink-jet head for continuous jet printing; the present invention is suitable for a jet-drawing machine to place an advertising board with a propaganda paint or a poster etc. for printing.
2. Description of the Prior Art
In markets, to get the goal of marketing of various commodities, people engaging in packaging and planning normally present the effect of advertisement with outdoor measures including a large stage background, an exhibition by illuminating or a car body advertising, and with indoor measures including small decorative paints, commodity display promotion and showcase display etc., in order that they can attract consumers' eye sights to achieve the object of sale.
As to the above stated various advertisements, people in the art normally use a jet-drawing machine to jet print on a soft thing such as a cloth or a paper. A jet printing structure “a” of the jet-drawing machine can be horizontally displaced on the machine, as shown in FIG. 7. It mainly comprises an ink box “b” and a micro-piezoelectric jet head “c”, these two are connected by means of a hose “d” fully filled with ink. When the jet head “c” has not yet be operated, the air pressure in the ink box “b” and the pressure of the atmosphere are in a balance state, hence the ink will not be jetted; when the jet head “c” jet prints outwards, the ink box “b” supplements ink for the jet head “c” to get the effect of jet printing.
Although the above stated jet printing structure “a” of the jet-drawing machine can get the effect of continuous jet printing on a soft material. By the fact that the soft material of a cloth or a paper is mounted on the jet-drawing machine in an inclined mode, the height of the ink box “b” is lower than that of the horizontal height of the jet head “c”, the entire jet printing structure “a” forms an angle. And in practical application, the cloth or the paper can be bent at will to be coincident with the angle required for jet printing. This will not make any inconvenience for the soft material. However, for a hard plane board unable to be curved, a situation results: a small plane board often drops during jet printing, while a large plane board is unable to be placed on the machine for jet printing. Therefore, it is a problem hard to deal by a conventional jet-drawing machine with such hard plane boards.